1. Field of the Invention
The invention relates generally to implanted or implantable blood pump systems, and more specifically, to a method and system for detecting the onset and/or presence of ventricular collapse associated with such pumps.
2. Description of Related Art
Generally, implantable blood pump systems are employed in either of two circumstances. First an implantable blood pump may completely replace a human heart that is not functioning properly, or second, an implantable blood pump may boost blood circulation in patients whose heart is still functioning although pumping at an inadequate rate.
For example, U.S. Pat. No. 6,183,412, which is commonly assigned and incorporated herein by reference in its entirety, discloses a ventricle assist device (VAD) commercially referred to as the “DeBakey VAD®”. The VAD is a miniaturized continuous axial-flow pump designed to provide additional blood flow to patients who suffer from heart disease. The device is attached between the apex of the left ventricle and the aorta. Proper blood flow through the device depends on an adequately filled ventricle and a positive differential pressure between the inlet and the outlet of the VAD pump.
Since this device produces flow continually and actively fills, it has the potential to create low pressure at the inflow in order to produce flow. “Excess Suction” occurs when the pressure in the inflow cannula decreases significantly—the pump begins to “suck” the ventricle closed, which would greatly reduce the pumping capability of the native heart and VAD. Decreasing the VAD's speed during an excess suction condition would allow the ventricle to refill, and normal blood flow to resume. Additionally, the detection of ventricular collapse and the ability to automatically adjust the pump's speed may aid in maintaining correct blood flow to the patient.
Excess suction may be caused by occlusion of the tip of the inflow cannula or by completely emptying the ventricle (ventricular collapse). In known pump systems, sustained excess suction typically triggers a diagnostic alarm on the pump controller. However, it would be desirable to detect the onset of suction prior to any physiologic effect. Additionally, it is typical of known methods that attempt to detect the onset or presence of ventricular collapse to use a binary “suction detect” flag when the onset of suction is believed to have been discovered. Information in addition to a simple binary indicator, however, is desirable as it would allow a physician or technician to make a more precise diagnosis.
The present invention addresses shortcomings associated with the prior art.